Snap action switch



Patented Oct. 10, 1950 SNAP ACTION SWITCH George 0. Pucrner, Indianapolis, Ind., assignor to P. It. Mallory & Co., Inc., Indianapolis, Ind., a

corporation of Delaware Application February 11, 1947, Serial No. 727,842

6 Claims.v (Cl. 20o-87) This invention relates to snap action switchesA and, more particularly to switches of the type which comprise an actuating member, an actuated member and a snap action spring interconnecting said members.

It is common practice, in snap action switches, to provide an actuated member carrying a movable contact which is adapted to be moved, by snap action, between a pair of flxed contacts or between a single fixed contact and a. stop member. In accordance with the prior art, a movable actuating member is provided for moving'a snap action spring which, in turn, effects snap action of the actuated or contact-carrying member. With such constructions, when the actuating member is moved to a rst critical positionthe direction of thrust of thesnap action spring is abruptly changed thereby moving-the actuated member and the movable contact thereon, by snap action, from its initial position to a second position. When the actuating member is moved to a second critical position, the direction of thrust of the actuating spring is again abruptly changed to return the movable contact to its initial position by snap action.

IIt was at first proposed to utilize a coil spring for obtaining the described snap action. However, the characteristics of such coil springs were not suiliciently uniform to provide reliable operation over extended periods of time. Further, such J coil springs were diiiicult to adjust and somewhat critical in operation. It was later found that the results could be considerably improved by substituting-a U-shaped snap action spring for the coil spring, this U-shaped spring being held in the actuating member are reached. Accordingly,

any irregularity in the function of the bearings is almost certain to cause faulty operation of the switch.

Prior to this invention, two types of bearings for the U-shaped snap action switch have been proposed. According to the rstproposal, a lost motion connection is provided at the bearing sur- 2 faces where the spring is connected to the actuating member and actuated member, respectively. The resulting relative movement between the snap action spring and the members to which it is secured is dlsadvantageous in that it tends to change the operating positions of the switch with resultant erratic operation thereof. The second proposal involves the use of so-.called knife edge bearings. According to this construction, tongues/ are provided at the respective ends of the snap action spring which nt into slots in the actuating has a iirst bearing surface or pivot line where one side of the member is engaged by the shoulders and a second pivot line where the other side of the member is engaged by the tongue at the innerend of the slot. These pivot lines are spaced apart a distance determined by the thickness of the member, the snap action spring pivoting on one of these bearing surfaces when the switch is in one part of its operating range and on the other bearing surface when the switch is in a different partof its operating range. This type of bearing d oes not function satisfactorily and is somewhat erratic in operation d-ue to the aforesaid double pivoting action. In addition, it has been found that such switches require a long wearing in period before satisfactory operation can even be approximated. l

It is an object of this invention to provide a snap action spring mounted in bearings in which the engaging surfaces of the spring and the members associated therewith define straight lines constituting, respectively, knife edges for the spring. y y

It is a further object of the invention to provide a snap action switch in which the spring pivots along a single straight line in each bearing.

It is a still further object of the invention to provide a snap action switchv in which complete satisfactory operation may be obtained without the necessity of operating the switch for a considerable wearing thereof.

It is a still further object of the invention to provide a switch which functions immediately when the actuating member reaches its respective ,critical positions.

The invention further contemplates the provision of a snap action switch which is simple in construction, of low cost, and reliable in operation over extended periods ofhtime.

in period before actual use ,Other objects of the invention will be apparent from the following description and accompanying drawings taken in connection with the appended claims.

The invention accordingly comprises the fea- A tures of construction, combination of elements, arrangement of parts, and methods of manufacture referred to above or which will be brought out and exemplified in the disclosure hereinafter set forth, including the illustrations in the drawings, the scope of the invention being indicated in the appended claims.

For a fuller understanding of the nature and objects of the invention as well as for specific fulfillment thereof, reference should be had to the following detailed description taken in connection with the accompanying drawings, in which:

Figure 1 is a perspective view of a novel' snap action switch;

Figure 2 is a plan view of the snap action switch shown in Figure 1;

Figure 3 is a sectional view taken along the line 3--3 of Figure 2; and l Figure 4 is a sectional view, partially broken away, taken along the line 4--4 of Figure 3. l

While a preferred embodiment of the invention is described herein, it is contemplated that considerable variation may be made in the method of procedure and the construction of parts without departing from the spirit of the invention. In n the following description and in the claims, parts will be identified by specific names for convenience, but they are intended to be as generic in their application to similar parts as the art will permit.

Referring now to the drawings in detail, the novel snap action switch comprises an actuated member I and an actuating member I| secured in a rivet type stack assembly I2 which is mounted on a support I3 as by a screw I4. The actuated member carries a movable contact I5 at the free end thereof which cooperates with fixed contact means I6. In the embodiment shown, the xed Contact means comprises a pair of xed stationary contacts I1, I8 which are mounted, respectively, on stationary contact arms I9. However, in some embodiments of the invention, only one fixed contact is utilized, such as a fixed contact I1, and the xed contact i8 may be replaced by a. suitable stop for limiting the movement of the actuated member I0.

Thecentral portion of the actuated member is cut out, as indicated at 20, and a bearing structure 2| is provided adjacent the free end thereof which will be more fully described hereinafter.

The actuating member il comprises a strip of resilient material which is mounted in the stack assembly I2 and a rigid member 26 is secured to the free end of the resilient strip 25 as by a rivet 21. An actuator is mounted in the rigid member 26 and this actuator preferably consists of an adjusting screw 28 having a bushing 29 for holding it in position and providing an additional mechanical connection between the rigid member 26 and the resilient strip 25. A lock nut is provided for fixing the adjusting screw in the bushing. A bearing structure 30, which is generally similar to bearing 2|,'is positioned at the free end of the actuating member and, as shown, a generally U-shaped snap action spring 3| is mounted in the bearings 2| and 30.

The bearing 30 comprises a pair of spaced projections 32 which define a slot 34 and these projections have iiat bearing surfaces35 on opposite sides of the slot. An ear 36 is struck up from substantially in alignment.

the rigid member 26 at the inner end of the slot and this ear has a pair of inclined surfaces 31, 33 each of which is disposed at an acute angle with respect to the bearing surfaces 35. In accordance with the invention, the surfaces 31, 33 define a knife edge 39 which is positioned in the plane of the flat bearing surfaces 35 and extends along theinner end of the slot 34.

The structure of the bearing 2| is generally similar to that of bearing 3U and this structure comprises a knife edge 42 defined by inclined surfaces 43, 44 of an ear 45 which is struck up from the actuated member I 0. The knife edge 42 extends along the inner edge of a slot 46 and lies in the plane of at bearing surfaces 41, 41 which are disposed at opposite sides of the slot.

The snap action spring '3| has tongues 50 at the respective opposite ends thereof, each tongue being anked by shoulders 5| which are spaced from the ends of the aforesaid tongues 50, respectively. These tongues are of the proper width to t into the respective slots 34 and 46 and, as shown by Figure 3, these tongue portions engage the knife edges 39 and 42, respectively. The shoulders 5| engage the respective bearing surfaces 35 and 41 and thereby hold the spring in position within the slots and against the knife edges 39 and 42. With respect to the bearing 2|, it will be seen that the line of engagement of the shoulders 5| with the bearing surfaces 41 is substantially in alignment with the knife edge 42 which engages the tongue 50, knife edge 42 being in the same plane with the bearing surfaces. Any misalignment between the knife edge 42 and the knife edge formed by the shoulders 5| of spring 3| aligned on the bearing surfaces 41 is caused by the thickness of thespring 3| which in the present invention is a minimum and is relatively small compared with the thickness of either the actuating member I l or the actuated member I0. Therefore, for all practical purposes the knife edge 42 and the other described knife edge for the concerned end of the spring 3| are Similarly, with respect to the bearing 30, the line of engagement of the shoulders v5| with the bearing surfaces 35 is in alignment with the knife edge 39 which engages the adjacent tongue 50. Accordingly, the engaging surfaces of the spring and the respective bearings define straight lines constituting, respectively, true knife edge bearings for the spring. Further, due to the angular position of the surfaces 31, 38 and 43, 44 only the knife edges 39, 42 of the respective struck up ears 36, 45 engage the spring in any position of the actuated member |0. As a result, the spring 3| rests on effectively true knife edge bearings and satisfactory operation of the switch is obtained without any wearing in period and without the assembly or the permanently fastening of the parts together.

It is important that the radius'r of the curved portion of the spring be less than half the distance D between the bearings in order that the legs of the U-shaped spring may be divergent so that the spring forces itself into engagement with the bearing surfaces thus holding the spring in assembled position at all times without the necessity of a permanent mechanical connection between the spring and the members I0 and With the parts in the positions` shown by Figure 3, upward movement of the actuator 28 to a first critical positionl causes the actuated member I0 to move downwardly by snap action thus opening contacts I5, |1 and closing contacts I5 and I8. Thereupon, downward movement of the actuator to a second critical position causes the actuated member I0 to move upwardly by snap action thus opening contacts I5, I8 and closing contacts I5 and II. During operation of the switch in this manner, the novel knife edge bearings of this invention cause the snap action spring 3| and actuated member III to move smoothly between their predetermined positions. Further, the fact that each bearing surface is effectively a single straight line prevents erratic operation of the switch and eliminates drift of the critical operating positions of the actuating member.

While the present invention, as to its objects and advantages, has been described herein as carried out in specific embodiments thereof. it is not desired to be limited thereby but it is intended to cover the invention broadly within the spirit and scope of the appended claims.

What is claimed as new and desired to be secured .by Letters Patent is:

1. In a snap action switch, an actuating member and an actuated member, each of said members having a slotted portion with fiat bearing surfaces at the respective sides of said slot, an inclined surface integrally formed of said members in said slotted portion, a knife edge being formed on said inclined surface disposed in the plane parallel to said bearing surfaces, a U- shaped snap action spring having tongues at the respective end thereof which extend through said slots and engage said knife edges, and shoulders formed on said spring for engaging said bearing surfaces whereby said spring engages each of said members along a line slightly oiset from one of said knife edges vertically and defined by the engaged portions of said shoulders and said bearing surfaces said offset being negligible as compared with the thickness of either one of said members.

2. In a snap action switch, an actuating member and an actuated member, each of said members having a fiat bearing surface with a central slot formed therein, struck-up means defining a knife edge which is positioned in the plane of said bearing surface and extends along the inner end of said slot, a snap action spring having, at each end thereof,.a tongue extending through one of said slots and engaging said knife edge, and shoulders at opposite sides of said tongue for engaging said bearing surface alonga line offset from said knife edge vertically a distance determined by the relatively small thickness of said spring compared with that of said actuating member.

3. In a snap action switch, an actuating member and an actuated member, a knife edge bearing on each of said members, and a snap action spring mounted in said bearings having a tongue at each end thereof which is flanked by side shoulder portions, each bearing comprising spaced projections having flat bearing surfaces thereon which are engaged, respectively, by the shoulders on said spring, and a struck up portion defining a knife edge which is positioned between and in the plane of said bearing surfaces, said knife edge being engaged by the tongue on said spring. whereby said spring intersects a plane defined by the knife edge and the line of engagement between said shoulders and said bearing surfaces.

4. In a snap action switch, an actuating member and an actuated member each having a slot therein andat bearing surfaces at opposite sides of each slot, a struck up ear at the inner end of each slot, each ear having inclined sur-v faces which are disposed, respectively, at acute angles with respect to said bearing surfaces thereby dening a knife edge extending along the inner end of said slot, said knife edge being disposed in the plane of said bearing surface, a snap action spring having tongues at the respective ends thereof which extend through said slots and engage said knife edges, and shoulders at opposite sides of said tongues, respectively, which engage said bearing surfaces along straight lines which are in a plane, respectively, with said knife edges.

5. In a snap action switch, an actuating member and an actuated member each having a slot therein and flat bearing surfaces at opposite sides of each slot, a struck up ear at the inner end of each slot, each ear having inclined surfaces which define a knife edge lying in the plane of said bearing surface, and a generally U- shaped snap action spring having tongues at the respective ends thereof which extend through said slots and engage said knife edges, and shoulders on said spring for engaging said bearing surfaces along straight lines which are in the same plane, respectively, with said knife edges, the surfaces defining said knife edges forming acute angles with the adjacent tongue portion of said' spring in all positions of the actuating member.

6. In a snap action switch, an actuated member carrying a movable contact, fixed contact means cooperating with said movable contact, an actuating member including a resilient spring and a rigid member attached to the free end of said spring arm, an actuator secured to said rigid member, spaced projections extending from said actuated member and said rigid member, respectively, said projections defining slots having fiat bearing surfaces at opposite sides thereof. a struck up ear at the inner end of each slot, each ear defining a knife edge lying in the plane of the adjacent bearing surfaces, and a generally U-shaped snap action spring having tongue portionswhich extend through said slots and engage said knife edges together with shoulders which engage said bearing surfaces, respectively, the engaging surfaces of said spring and said members dening straight lines constituting, respectively, knife edge bearings for said spring.

' GEORGE O. PUERNER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,038,098 Carlson Apr. 21, 1936 2,237,705 Kohl Apr. 8, 1941 2,402,838 Obszarny June 25, 1946 2,418,068 Cornelius Mar. 25. 1947 2,429,074 Rugh Oct. 14, 1947 2,458,518 Kohl Jan. l1, 1949 

